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Identification of the major in vivo ABl-42-degrading catabolic-system in brain parenchyma.

脑实质中主要的体内ABl-42降解分解代谢系统的鉴定。

基本信息

批准号：
12672167
负责人：
IWATA Nobuhisa
金额：
$ 2.5万
依托单位：
The Institute of Physical and Chemical Research
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

Accumulation of amyloid-pβ peptide (Ap) in brain triggers the pathological cascade leading to Alzheimer' s disease. To examine the mechanism of AB catabolism, we analysed the fate of multiply radio-labeled 3H/14C-Aβl-42 injected into rat hippocampus and identified neutral endopeptidase (s) similar or identical to neprilysin as the rate-1imiting peptidase using a panel of peptidase inhibitors. Chronic infusion of thiorphan, a specific inhibitor of neprilysin, into rat hippocampus caused accumulation of endogenous AB. To further identify the thiorphan-sensitive peptidase, we analysed ABl-42 catabolism by six recombinant thiorphan-sensitive peptidases in neutral endopeptidase family. Neprilysin degraded AB most rapidly and efficiently among them. Neprilysin-deficient mice showed significantly reduced ability to catabolize AB. We also observed a gene dosage-dependent clevation of the endogenous AB levels (-/- > +/- > +/+) in the mouse brains. The increase in the AB42 level in the neprilysin-deficient mouse brain was comparable to that in the mice carrying PSI mutation. Moreover, the regional Ap levels in wild-type mouse brain were in the order of hippocampus > cortex > striatum/thalamus > cerebellum and this tendency was markedly exaggerated in the neprilysin-deficient mice. In the experiments using aged mice, neprilysin activity and its protein content in hippocampus were reduced by 200% at 30 months-old ages, compared to 2 months-old ages. The neprilysin activity in cortex was also slightly but significantly reduced with aging, whereas those in other regions were not changed. These observations suggest that the neprilysin is the major AB-degrading enzyme in brain despite the molecular redundancy of the neprilysin family and that reduction of neprilysin activity particularly in the regions vulnerable to AB pathology will contribute to Alzheimer' s disease development by promoting AB deposition.

淀粉样β肽（amyloid-pβ peptide，Ap）在脑内的蓄积是导致阿尔茨海默病（Alzheimer' s disease，AD）的病理级联反应。为了研究AB catalysts的机制，我们分析了注射到大鼠海马中的多重放射性标记的3 H/14 C-A β 1 -42的命运，并使用一组肽酶抑制剂鉴定了与脑啡肽酶相似或相同的中性内肽酶作为限速肽酶。慢性输注thiorphan，脑啡肽酶的特异性抑制剂，到大鼠海马引起内源性AB的积累。为了进一步鉴定噻吩敏感肽酶，我们分析了ABl-42催化剂，通过中性内肽酶家族中的六种重组噻吩敏感肽酶。其中Neprilysin降解AB最迅速和有效。Neprilysin缺陷小鼠表现出显著降低的分解AB的能力。我们还观察到小鼠脑中内源性AB水平的基因剂量依赖性升高（-/- > +/- > +/+）。脑啡肽酶缺陷小鼠脑中AB 42水平的增加与携带PSI突变的小鼠相当。此外，野生型小鼠脑中的区域Ap水平的顺序为海马>皮质>纹状体/丘脑>小脑，并且这种趋势在脑啡肽酶缺陷小鼠中明显夸大。在使用老年小鼠的实验中，与2个月大的小鼠相比，30个月大的小鼠海马中的脑啡肽酶活性及其蛋白质含量降低了200%。大脑皮层脑啡肽酶活性随年龄增长而显著降低，而其他区域脑啡肽酶活性无明显变化。这些观察结果表明，脑啡肽酶是脑中主要的AB-降解酶，尽管脑啡肽酶家族的分子冗余，并且脑啡肽酶活性的降低，特别是在易受AB病理影响的区域中，将通过促进AB沉积而有助于阿尔茨海默病的发展。